fix(capture): Ensure download filename has the correct extension. (#5691)

extensions/cornerstone/src/utils/CornerstoneViewportDownloadForm.tsx

@@ -215,7 +215,7 @@ const CornerstoneViewportDownloadForm = ({
     }
   }, [viewportDimensions, showAnnotations]);
 
-  const handleDownload = async (filename: string, fileType: string) => {
+  const handleDownload = async (baseFilename: string, fileType: string) => {
     const divForDownloadViewport = document.querySelector(
       `div[data-viewport-uid="${VIEWPORT_ID}"]`
     );
@@ -225,8 +225,9 @@ const CornerstoneViewportDownloadForm = ({
       return;
     }
 
+    const filename = `${baseFilename}.${fileType}`;
     const canvas = await html2canvas(divForDownloadViewport as HTMLElement);
-    downloadUrl(canvas.toDataURL(`image/${fileType}`, 1.0));
+    downloadUrl(canvas.toDataURL(`image/${fileType}`, 1.0), { filename });
   };
 
   const ViewportDownloadFormNew = customizationService.getCustomization(